It has become desirable to impart a visual pattern or other patterned effect on some types of fabrics. For example, it is desireable to produce a washed-out, distressed, or pre-worn effect on dyed denim fabrics. Dyeing and dye printing are normally additive processes where dyes or pigments are added to natural, white, or previously dyed fabrics. Creating distressed or pre-worn surface effects is generally a subtractive process of removing color from the dyed fabric. Several subtractive, dyed fabric treatment processes are known in the art, but have been found to be unsatisfactory for various reasons.
For example, discharge printing is a subtractive printing process where fabric is piece-dyed and then printed with a paste of caustic soda and sodium hydrosulfite to destroy the color in the printed areas. The caustic paste used to remove the base color must be thoroughly washed out, or it can have a serious deteriorating effect on the fabric.
Acid washing is a chemically induced, subtractive process which removes color from fabric already cut and sewn into garments. Acid washed effects are achieved by soaking pumice stone in chlorine bleach, which are then added to a load of denim garments in an industrial washing machine without water. The load of stones and garments is agitated for a length of time based upon the degree of "frosting" or color removal desired, e.g. from one to several hours. The effect of the acid coupled with the abrasion caused by the stones is extremely detrimental t fabric strength and durability.
Stone washing is a mechanical, color subtractive process achieved by a combination of crocking, abrasion, and lack of color fastness to washing. Here denim garments are loaded into industrial washers along with water and pumice stones and agitated for a predetermined length of time. The degree of washout can be somewhat controlled by the length of the agitation cycle, however, the overall effect is the end result of substantially random processes. The fabric is subject to less abuse and deterioration in stone washing than in acid washing. However, for both stone and acid washing, the washout patterning of the fabric cannot be precisely controlled and made repeatable from load to load. In both cases the wash equipment is subjected to extremely hard beating caused by the tumbling and crumbling of the pumice stone
Acid washing and other chemical treatment of fabrics generate large amounts of contaminated or caustic effluents which are discharged to the environment. It is highly desireable to find ways to reduce the amounts of polluted effluents that are discharged to the environment.
In order to overcome the disadvantages of the prior art, it is a principal object of the invention to provide an apparatus and related method for producing a visual pattern or other effect on fabric which minimizes abuse and deterioration of the process equipment, as well as the fabric being processed. In particular, it is a specific object to obtain subtractive color patterning of woven fabric by non-caustic fluid treatment which does not wear down and damage the process equipment and deteriorate the fabric. It is a further object to pattern fabric through a process which reduces the amounts of polluted effluents that are discharged to the environment.